Pyran-4-ones y-Pyrones

Reactions with electrophiles occur more readily at the carbonyl oxygen atom than is the case for pyran-2-ones. Hydrogen chloride, for example, yields aromatic 4-hydroxypyrylium chlorides (4.2) when reacted with 2,6-disubstituted pyran-4-ones. 

Nucleophilic attack follows a similar pattern to that encountered with pyran-2-ones thus hydroxyl ion attacks in conjugate fashion at C-2. In 

Tho word vinylogous iefe - t j th presence Ejf CH=CH ( inyfl unrt between two atoms Of groups, an O and C=0 in this case, relaying trie propertiefi ot lo the otlier. 

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